Upgrading catalytic c5 hydrocarbons



Nov. 1, 1960 o. L. BAEDER UPGRADING CATALYTIC c HYDROCARBONS Filed Dec.20, 1956 Donald L. Baedel Inventor By K CW Afiorney United States Patent2,958,718 UPGRADING CATALYTIC C HYDROCARBONS Donald L. Baeder, Fanwood,'N.J., assignor to Esso Research and Engineering Company, acorporationof Delaware Filed Dec. 20,- 1956, Ser. No. 629,508 6 Claims.(Cl. zen-683:9

pression ratio. At the present time the compression ratio of currentautomobile engines has been increased to values above 6.5, rangingupwardly to as high as 12. Engines having such high compression ratiosrequire use of high anti knock gasolines. The more extended use ofautomatic transmissions has also aggravated the problem of satisfyingthe octane requirements of current automotive engines. In the past,octane ratings of gasolines have primarily been determined by ASTM test,designated D908-47T. vWhile this is an important and valuable anti-knockrating test, it has'become appreciated that the Research octane ratingof a gasoline as determined by this method correlates poorly with actualroad performance of a gasoline. This is true in part since the Researchoctane number is determined in a test pro cedure at which the engine isoperated at conditions of constant speed and constant load. As opposedto this, the actual knocking tendency of a fuel in road performance isgreatest during maximum load. It is therefore appreciated at this timethat the Research octane number rating of a gasoline is not a completeindication of the value of a gasoline in satisfying an engine under roadconditions.

i As a result, other methods of determining octane ratings are commonlyemployed. One such method is the so-called motor method test, designatedby ASTM test Method D357-47. It has been found that the motor methodoctane determination correlates with the road performance of a gasolinesomewhat better than the Research octane rating.

;In view of these basic factors, production of present day high qualitygasolines must be carried out with reference to both the Research andMotor method octane rating. The over-all octane rating of the fuel issome fraction through a molecular sieve adsorption zone so as to removetherefrom substantially all the normal hydrocarbons. The normalhydrocarbon-free effluent from the tained from conventional catalyticcracking of petroleum g'as oils; This fraction typically boils in,the'range of 75 3 to 115.F. and 'contains's'ome C s. A typicalcomposition is as follows:'

Analysis of typicdllliayt own) catalytic C5 stream Vol. percent ButanesV 0.6 Butenes 2.6 Isopentane 42.2 n-Pent-ane 5.0 =2-methylbutene-1 11.6Pentene-fl 7.6 Cis-pentefie-Z 5.8 tnans-pentene-2 9.2 2-methylbutene-215.0 Pentadienes 0.4

The molecular sieves utilized are known. The scientific and patentliterature contains numerous references to the sieving action of naturaland synthetic zeolites. Among the natural zeolites having this sievingproperty may be mentioned chabazites. A synthetic zeolite with molecularsieve properties is described in US. Patent 2,424,191. Zeolites varysomewhat in composition but generally contain the elements silicon,aluminum, and oxygen as well as an alkali metal and/or an alkaline earthmetal element, e.g., sodium and/0r calcium. The naturally occurringzeolite, analcite, for instance, has the empirical formula NaAlSi- O .HO. Barrer, U.S. Patent 2,306,610, teaches that all or part of the sodiumis replaceable by calcium to yield, on dehydration, a molecular sievehaving the formula (Ca.Na Al Si O Black, US. Patent 2,522,426, describesa synthetic molecular sieve zeolite having the formula 4CaO.A1 'O .4SiOA large number of other naturally occurring zeolites having molecularsieve activity, i.e., the ability to adsorb straight chain hydrocarbonsand exclude the branch chain isomers due to differences in molecularsize, are known. The pores in different zeolites may vary in diameterfrom less than 3 or 4 to 15 'or more Angstrom units, but for any onezeolite the pores are substantially of uniform size. It is preferred touse zeolites having pore openings of about 5 Angstroms, e.g., calciumalumino silicates.

In general the molecular sieve contacting operation is carried out inthe vaporphase at 250 to 350 F. depending on boiling point of feed. The.v./l1r./v. is about 0.5 to 1. The operation is continued until the sieveis saturated with adsorbate (about 10-12 wt. percent on sieve). Theadsorbate can be removed by a selective desorbent such as propylenewhich is then separated from the adsorbent by'simple distillation. Itcan also be removed by raising the sieve temperature to 600 F. andlowering the pressure to 50 mm. Thefir'sttech nique is preferred sinceat 600 F."some polymerization of n-olefins can occur. x

i The contacting of the, feed with the molecular sieve in the adsorptbnzone is conducted so as to remove frOmthe feed substantially all (95 to98 ,wt. percent) the normal hydrocarbons. v t

The normal hydrocarbon-free ,eflluent is withdrawn.

' This effluent is then hydrogenated for complete saturaof hydrogenationcatalysts m ay'beemployed. Preferred tion over a hydrogenation catalyst.

In, conducting the hydrogenation of the eflluent fraction in accordancewith this invention, a wide variety catalysts constitute the oxides ofcobalt or molybd Patented Nov. 1, 1.960.

in admixture and including cobalt molybdate. Other catalytic agentswhich can be used are platinum or nickel. Preferably these catalyticagents are supported on an adsorbent support such as alumina. It isparticularly preferred to employ cobalt molybdate as the catalyst. Thepressure employed is to be in the range of 25 to 500 pounds per squareinch although it is preferred to use pressures below 400 p.s.i.g. forthe hydrogenation of the efiluent and it is particularly desirable toemploy a pressure of about 200 p.s.i.g. Throughputs of 1 to 2 v./v./hr.may be employed although the preferred range is about 5 to v./v./hr. Thetemperature maintained during hydrogenation is about 500 to 800 F. andspecifically 700 F. Contact of the efliuent with the catalyst underthese conditions should be carried out employing a rate of hydrogensupply above about 1000 standard cubic feet of hydrogen per barrel, andgenerally about 2500 standard cubic feet per barrel.

The specific hydrogenation conditions are to be selected from theforegoing limits by regard to the resulting olefin saturation and/orhydrogen consumption. In general, for hydrogenation for completesaturation, hydrogen consumptions of about 450 to 600 standard cubicfeet per barrel will be employed. In treating a typical effluent forcomplete olefin saturation, a hydrogen consumption of at least about 500s.c.f./b. is ordinarily required.

The advantages of this invention will be better understood by referenceto the following example and flow diagram.

Referring now to the flow diagram, a Baytown catalytic C feed is fedthrough line 1 to a 5 Angstrom molecular sieve adsorption zone 2. Theadsorbent may be arranged on trays or packed therein with or withoutsupports. One adsorption zone has been shown for simplicity, but two ormore can be used. The feed is at a temperature of 250 F. in the vaporphase and the flow rate is 0.5 v./v./hr. The feed had an initialResearch octane number of 102.2 and a motor octane number of 88.3.Substantially all, e.g., 31 volume percent on feed of the normalhydrocarbons are adsorbed on the adsorbent in zone 2.

The efiiuent, free of normal hydrocarbons, is withdrawn from adsorptionzone 2 through line 5 to hydrogenation zone 6. This efiiuent prior tothe hydrogenation has a Research octane number of 103.5 and a motoroctane number of 95. In hydrogenation zone 6 the efliuent ishydrogenated at a temperature of 700 F. in the vapor phase over a cobaltmolybdate on alumina catalyst. This efiluent which contains about 38.5vol. percent olefins is thus completely saturated. The conditions inhydrogenation zone 6 are a pressure of 200 p.s.i.g., a throughput of 2v./hr./v. with a hydrogen consumption of about 150 s.c.f./b. Thehydrogenated efiluent is withdrawn through line 7 at a 70% yield onoriginal total C feed. Its Research octane number is 104.2 and its motoroctane number is 100.0. This latter figure represents a marked increase.

The adsorbate on the molecular sieve is desorbed by the addition ofpropylene also at 250 F. Feed rate is 0.5 v./hr./v. The adsorbate isseparated from the propylene by simple distillation and contains thefollowing materials in the indicated yields.

Adsorbate: Yield on feed n-Pentane 5.0

n-Pentene-l 7.6 Cis Pentene-Z 5.8

Transpentene-Z 9.2 Pentadiene 0.4 C438 3.2

This adsorbate is about 75% olefinic and can be utilized as a feed forchemicals. Because of the normal character of the olefins they areexcellent feeds for making alcohols, aldehydes, ethers and thereforecommand a high price.

The advantages of this invention will be apparent to the skilled in theart. A significant motor octane number improvement is obtained withoutthe necessity of hydrogenating the total feed. Further, hydrogenation ofthe total feed would not produce a gasoline blending stock with bothhigh Research and Motor octane number. This is due to the fact that theResearch octane number of normal olefins are degraded on hydrogenation.The motor octane number in only slightly improved. This is shown asfollows:

Research +8 ml. TEL

n-pentane 83. 6

Since all of the C olefins in the adsorbate (31% on feed) would beconverted to n-pentane, it is obvious that the octane number obtained byhydrogenation of the total C feed would be inferior to the octaneobtained by selective separation fol-lowed by hydrogenation of the isoparafiinisoolefin fraction. Thus this octane improvement is obtained withmarked efiiciencies in hydrogen use and equipment size.

It is to be understood that this invention is not limited to thespecific examples which have been ofiered merely as illustrations andthat modifications may be made without departing from the spirit of theinvention.

What is claimed is:

1. A process for upgrading a catalytic C hydrocarbon fraction containingisopentane, n-pentane, Z-methylbutene-l, pentene-l, cis-pentene-2,trans-pentene-Z, and 2-methylbutene-2, which comprises the steps ofpassing the fraction through a molecular sieve adsorption zone so as toremove therefrom substantially all the normal hydrocarbons n-pentane,pentene-l cis-pentene-2 and trans-pentene-Z; withdrawing the normalhydrocarbonfree efiluent from the adsorption zone and hydrogenating theeffluent for complete saturation of the Z-methylbutene- 1 and the2-methylbutene-2 therein in the presence of a hydrogenation catalyst.

2. The process of claim 1 in which the molecular sieve has p'oreopenings of about 5 Angstroms.

3. The process of claim 2 in which the molecular sieve contacting stepis carried out in the vapor phase at a temperature in the range of 250to 350 F. and a feed rate of 0.5/l v./v./hr.

4. The process of claim 3 in which the C hydrocarbon fraction has aboiling point in the range of 75 to F.

5. The process of claim 4 including the additional step of desorbing thenormal hydrocarbons from the sieve by treatment with propylene.

6. The process of claim 2 in which the molecular sieve is a calciumalumino silicate.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Brooks et al.; The Chemistry of Petroleum Hydrocarbon, vol.3, pages 121 and 331-2, May 16, 1955.

Nelson et al.: Analytical Chemistry, vol. 29, pages 1026- 1029, July1957.

1. A PROCESS FOR UPGRADING A CATALYTIC C5 HYDROCARBON FRACTIONCONTAINING ISOPENTANE, N-PENTANE, 2-METHYLBUTENE-1, PENTENE-1,CIS-PENTENE-2, TRANS-PENTENE-2, AND 2-METHYLBUTENE-2, WHICH COMPRISESTHE STEPS OF PASSING THE FRACTION THROUGH A MOLECULAR SIEVE ADSORPTIONZONE SO AS TO REMOVE THEREFROM SUBSTANTIALLY ALL THE NORMAL HYDROCARBONSN-PENTANE, PENTENE-1 CIS-PENTENE-2 AND TRANS-PENTENE-2, WITHDRAWING THENORMAL HYDROCARBONFREE EFFLUENT FROM THE ADSORPTION ZONE ANDHYDROGENATING THE EFFLUENT FOR COMPLETE SATURATION OF THE2-METHYLBUTENE1 AND THE 2-METHYLBUTENE-2 THEREIN IN THE PRESENCE OF AHYDROGENATION CATALYST.